Method and system for feedback of antenna beamforming

ABSTRACT

The disclosed systems and methods achieve improved communication by periodically sending sounding packets from a transmitter; feeding back, from a receiver, the change in beamforming estimation according to reception of the sounding packets; and utilizing the change in beamforming estimation to produce transmitter beamforming.

RELATED APPLICATIONS

The present U.S. Utility Patent Application claims priority pursuant to35 U.S.C. §120, as a continuation, to the following U.S. Utility PatentApplication which is hereby incorporated herein by reference in itsentirety and made part of the present U.S. Utility Patent Applicationfor all purposes:

1. U.S. Utility application Ser. No. 11/342,427, entitled “METHOD ANDSYSTEM FOR ANTENNA BEAMFORMING,” filed Jan. 30, 2006, pending, whichclaims priority pursuant to 35 U.S.C. §119(e) to the following U.S.Provisional Patent Application which is hereby incorporated herein byreference in its entirety and made part of the present U.S. UtilityPatent Application for all purposes:

-   -   1.1. U.S. Provisional Application Ser. No. 60/738,504, entitled        “METHOD AND SYSTEM FOR ANTENNA BEAMFORMING,” filed Nov. 21,        2005, now expired.

FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[Not Applicable]

MICROFICHE/COPYRIGHT REFERENCE

[Not Applicable]

BACKGROUND OF THE INVENTION

Multiple antennas can be used to i) increase the antenna gain bybeamforming; ii) provide diversity gain through some form of antennacombining; iii) increase the data rate by spatial multiplexing; and iv)suppress spatial interference by null steering. However, a system withmultiple antennas may be unable to take advantage of all of thesebenefits if the system cannot accurately estimate and track a wirelesscommunications channel.

Further limitations and disadvantages of conventional and traditionalapproaches will become apparent to one of skill in the art, throughcomparison of such systems with some aspects of the present invention asset forth in the remainder of the present application with reference tothe drawings.

BRIEF SUMMARY OF THE INVENTION

A system and/or method is provided for antenna beamforming,substantially as shown in and/or described in connection with at leastone of the figures, as set forth more completely in the claims.Advantages, aspects and novel features of the present invention, as wellas details of an illustrated embodiment thereof, will be more fullyunderstood from the following description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of an exemplary system for antenna beamformingin accordance with an embodiment of the present invention; and

FIG. 2 is a flowchart illustrating an exemplary method for antennabeamforming in accordance with a representative embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

Aspects of the present invention relate to antenna beamforming and morespecifically, to steady state parameter feedback systems and methods.Although the following description may refer to particular wirelesscommunication standards, many other standards may also use these systemsand methods.

Multiple-input multiple-output (MIMO) techniques take advantage ofmultiple transmit and/or receive antennas for communication. Forexample, the UMTS/W-CDMA standard specifies transmit diversity, and the802.11n wireless local area network (WLAN) standard specifies spatialdivision multiplex. Spatial multiplexing and spatial diversity are twocategories of MIMO systems.

Spatial division multiplexing (SDM) occurs when several streams aretransmitted simultaneously from the multiple transmit antennas tomultiple receive antennas to boost the spectral efficiency of thetransmission. SDM may be fully exploited if the number of antennas is,at both sides, equal to or greater than the number of parallel streams.

Spatial diversity occurs when the same symbols are transmitted ondifferent transmit antennas or received by several receive antennas.Diversity combining may be a form of beamforming where the signaltransmitted or received by the antenna array may be weighted in phaseand in amplitude.

Spatial processing may be combined with orthogonal frequency divisionmultiplexing (OFDM). OFDM multi-carrier transmission is used in manystandards (e.g. WiFi 802.11 and WiMAX 802.16). The spatial processing ofthe current invention may be applied per sub-carrier (frequency-domainprocessing), thereby decoupling the spatial processing from theequalization of the frequency-selective channel and leading to lowcomplexity solutions. MIMO processing can be performed at either thetransmitter or the receiver side, or at both sides.

FIG. 1 is an illustration of an exemplary system 100 for antennabeamforming in accordance with an embodiment of the present invention.The system 100 comprises a transmitter 101 and a receiver 103. Thetransmitter 101 comprises Ntx antennas and the receiver 103 comprisesNrx antennas.

The transmitter 101 sends Nss streams 105 of sounding packets. A streamof sounding packets is a periodic transmission of a sequence known bythe receiver 103. The periodicity may be, for example, at a rate of 1kHz.

Upon receiving a first plurality of sounding packets at time T, thereceiver 103 may generate a channel estimate matrix H(T), from which abeamforming estimate matrix V(T) may be acquired. The beamformingestimate matrix V(T) contains Ntx rows and Nss columns. Alternatively,the receiver 103 may generate a channel estimate matrix H(T) withcontains Nrx rows and Ntx columns. The relationship between H and V isH=U×S×V′, where V′ is the complex conjugate transpose of V, S withdimensions Nss X Nss, where Nss is the number of streams, and U withdimensions Nrx X Nss may be used for receiver beamforming.

Upon receiving a second plurality of sounding packets at time TΔT, thereceiver 103 may generate a beamforming estimate matrix V(T+ΔT). Thereceiver 103 generating a feedback signal ΔV=V(TΔT)−V(T). The feedbacksignal is used to perform transmit beamforming. The feedback signal issent to the transmitting station and will usually be able to berepresented by a smaller number of bits. Alternatively, the beamformingestimate matrix V can be a function of an angle V=fΘ), and the change inthe angle ΔΘ.) can be used as feedback, where ΔΘ.=ΘT+ΔT)−Θ(T). Forexample, a 2×2 beamforming matrix may be represented as:

$\quad\begin{bmatrix}{\cos (\Theta)} & {\sin (\Theta)} \\{- {\sin (\Theta)}} & {\cos (\Theta)}\end{bmatrix}$

Each element of the 2×2 beamforming matrix may be quantized.Alternatively, the angle Θ may be quantized, thereby representing the2×2 beamforming matrix by a single parameter. Each beamforming matrixmay also be represented by a set of angles, denoted by Θ.

When the first beamforming estimate and the second beamforming estimateare substantially the same, the feedback signal may not be sent to thetransmitter. Alternatively, when the first beamforming estimate and thesecond beamforming estimate are substantially the same, the feedbacksignal may be a single bit indicating that the first beamformingestimate and the second beamforming estimate are substantially the same.

FIG. 2 is a flowchart 200 illustrating an exemplary method for antennabeamforming in accordance with a representative embodiment of thepresent invention.

A first plurality of sounding packets is received at 201. According tothe first set of sounding packets, a first beamforming estimate matrixis generated at 203. A second plurality of sounding packets is receivedat 205. According to the second set of sounding packets, a secondbeamforming estimate matrix is generated at 207. The difference betweenthe first beamforming estimate matrix and the second beamformingestimate matrix is fed back at 209 for transmitter beamforming.

The present invention may be realized in hardware, software, or acombination of hardware and software. The present invention may berealized in a centralized fashion in an integrated circuit or in adistributed fashion where different elements are spread across severalcircuits. Any kind of computer system or other apparatus adapted forcarrying out the methods described herein is suited. A typicalcombination of hardware and software may be a general-purpose computersystem with a computer program that, when being loaded and executed,controls the computer system such that it carries out the methodsdescribed herein.

The present invention may also be embedded in a computer programproduct, which comprises all the features enabling the implementation ofthe methods described herein, and which when loaded in a computer systemis able to carry out these methods. Computer program in the presentcontext means any expression, in any language, code or notation, of aset of instructions intended to cause a system having an informationprocessing capability to perform a particular function either directlyor after either or both of the following: a) conversion to anotherlanguage, code or notation; b) reproduction in a different materialform.

While the present invention has been described with reference to certainembodiments, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted withoutdeparting from the scope of the present invention. In addition, manymodifications may be made to adapt a particular situation or material tothe teachings of the present invention without departing from its scope.Therefore, it is intended that the present invention not be limited tothe particular embodiment disclosed, but that the present invention willinclude all embodiments falling within the scope of the appended claims.

What is claimed is:
 1. A transmitter within a communication system,comprising: a plurality of antennas for: transmitting a first pluralityof sounding packets to a receiver; transmitting a second plurality ofsounding packets to the receiver; and receiving a feedback signal fromthe receiver, the feedback signal being generated by the receiver basedon a difference between a first beamforming estimate determined based onthe first plurality of sounding packets and a second beamformingestimate determined based on the second plurality of sounding packets;and a processor for configuring beamforming of the plurality of antennasbased on the feedback signal; wherein the feedback signal includes onlya single bit when the first beamforming estimate and the secondbeamforming estimate are substantially the same; wherein the feedbacksignal includes multiple bits when the first beamforming estimate andthe second beamforming estimate differ.
 2. The transmitter of claim 1,wherein the feedback signal is indicative of the change in one or moreparameters between the first beamforming estimate and the secondbeamforming estimate.
 3. The transmitter of claim 2, wherein the firstbeamforming estimate and the second beamforming estimate are functionsof one or more angles of a sounding packet in the first and secondplurality of sounding packets and the one or more parameters include theone or more angles.
 4. The transmitter of claim 1, wherein the firstbeamforming estimate and the second beamforming estimate are beamformingestimation matrices.
 5. The transmitter of claim 1, wherein the firstbeamforming estimate is acquired from a first channel estimate matrixbased on the first plurality of sounding packets and the secondbeamforming estimate is acquired from a second channel estimate matrixbased on the second plurality of sounding packets.
 6. The transmitter ofclaim 1, wherein the communication system is a Multiple-InputMultiple-Output (MIMO) system, the plurality of antennas includes aplurality of transmit antennas and the receiver further includes aplurality of receive antennas.
 7. The transmitter of claim 6, whereineach of the first plurality of sounding packets and the second pluralityof sounding packets includes multiple streams of sounding packetstransmitted over the plurality of transmit antennas and received overthe plurality of receive antennas.
 8. The transmitter of claim 7,wherein each of the multiple streams is a periodic transmission of asequence of known by the receiver.
 9. The transmitter of claim 7,wherein each of the first beamforming estimate and the secondbeamforming estimate are beamforming estimate matrices having a numberof rows corresponding to a number of transmit antennas and a number ofcolumns corresponding to a number of streams.
 10. The transmitter ofclaim 6, wherein each of the first beamforming estimate and the secondbeamforming estimate are beamforming estimate matrices having a numberof rows corresponding to a number of receive antennas and a number ofcolumns corresponding to a number of transmit antennas.
 11. Thetransmitter of claim 1, wherein the first plurality of packets aretransmitted at a first time and the second plurality of packets aretransmitted at a second time subsequent to the first time.
 12. A methodfor improving communication, wherein the method comprises: transmittinga first plurality of sounding packets from a transmitter to a receiver;transmitting a second plurality of sounding packets from the transmitterto the receiver; and receiving a feedback signal at the transmitter fromthe receiver, the feedback signal being generated by the receiver basedon a difference between a first beamforming estimate determined based onthe first plurality of sounding packets and a second beamformingestimate determined based on the second plurality of sounding packets;and configuringbeamforming of the transmitter based on the feedbacksignal; wherein the feedback signal includes only a single bit when thefirst beamforming estimate and the second beamforming estimate aresubstantially the same; wherein the feedback signal includes multiplebits when the first beamforming estimate and the second beamformingestimate differ.
 13. The method of claim 12, wherein the firstbeamforming estimate and the second beamforming estimate are in the formof a matrix.
 14. The method of claim 13, wherein the first beamformingmatrix is based on a channel according to the first plurality soundingpackets.
 15. The method of claim 14, wherein the second beamformingmatrix is based on a channel according to the second plurality soundingpackets.
 16. The method of claim 12, wherein the feedback signal isbased on a difference between one or more angles in the firstbeamforming estimate and one or more angles in the second beamformingestimate.
 17. The method of claim 12, wherein the communication systemis a Multiple-Input Multiple-Output (MIMO) system, the transmitterincludes a plurality of transmit antennas and the receiver includes aplurality of receive antennas.
 18. The method of claim 17, wherein eachof the first plurality of sounding packets and the second plurality ofsounding packets includes multiple streams of sounding packetstransmitted over the plurality of transmit antennas and received overthe plurality of receive antennas.
 19. The method of claim 12, whereinthe first plurality of packets are transmitted at a first time and thesecond plurality of packets are transmitted at a second time subsequentto the first time.
 20. A transmitter within a communication system,comprising: a plurality of antennas for: transmitting a first pluralityof sounding packets to a receiver; transmitting a second plurality ofsounding packets to the receiver; and receiving a respective feedbacksignal from the receiver, the feedback signal being generated by thereceiver based on a difference between a first beamforming estimatedetermined based on the first plurality of sounding packets and a secondbeamforming estimate determined based on the second plurality ofsounding packets; and a processor for configuring beamforming of theplurality of antennas based on the feedback signal; wherein the feedbacksignal is based on a difference between one or more angles in the firstbeamforming estimate and one or more angles in the second beamformingestimate; wherein the feedback signal includes only a single bit whenthe first beamforming estimate and the second beamforming estimate aresubstantially the same; wherein the feedback signal includes multiplebits when the first beamforming estimate and the second beamformingestimate differ.